LONG DISTANCE REFLECTIVE SWITCH EMPLOYED IN WIND TURBINES FOR RPM SENSING

Providing alternative energy design engineers with a means of reliably and accurately detecting the speed of wind turbines, TT electronics OPTEK Technology’s OPB732 Series long distance infrared reflective switch has been employed in a 6kW wind turbine for RPM sensing. Placed at the turbine rotor, the switch is used internally to sense RPMs, and that data is then transmitted to a customer-accessible Web site via GPRS.“The ability to accurately monitor turbine RPMs is crucial for their safe and efficient operation,” said Alan Bennett, vice president of worldwide sales for OPTEK Technology. “With its non-contact design, which features an emitter and sensor protected from contaminants by a clear window, the OPB732 reflective switch provides the reliability and accuracy necessary for this application.”In addition to wind turbines, the OPB732 reflective switch is ideal for use in assembly line and machine automation, equipment security, door sensor, machine safety, end of travel sensor, and non-contact reflective object sensor applications.The OPB732 Series switch has a reflective distance of more than one inch, depending on circuitry.  The reflective switch configuration includes an infrared LED and phototransistor, and uses an opaque housing to reduce the sensor’s ambient light sensitivity.When infrared light strikes the phototransistor, it becomes forward biased and is considered to be in the “on” state, providing an IC(ON) current proportional to the light striking the phototransistor.  When the infrared light from the LED is not reflected to the phototransistor, the device turns “off,” minimizing the IC(ON) current.The OPB732 Series infrared LED features an 850nm wavelength and a power dissipation of 100mW.  Maximum forward current is 50mA and maximum forward voltage is 1.8V (If=20mA).  Reverse DC voltage is 3V, with reverse current of 100µA (Vr=2.0V). The output phototransistor features collector-emitter voltage of 30V, collector DC current of 50mA, and power dissipation of 100mW.  Operating temperature range for the long distance reflective switch is -40°C to +85°C.  The OPB732 Series assembly is offered with PC board through-hole pins or 24”, 26 AWG wires.  The phototransistor can be configured as a common collector or common emitter device.